Phosphoric acid esters of nitroalcohols



Patented Oct. 31, 1939 PATENT OFFICE PHOSPHORIC ACID ESTEBS OF NITROALCOHOLS Byron M. Vanderbilt, to Commercial Terre Haute, Ind., assignor Solv ents Corporation, Terre Haute, Ind., a corporation at Maryland No Drawing.

Application May 19, 1938,

Serial No. 208,879

5 Claims.

My invention relates to new phosphoric acid esters of aliphatic nitroalcohols and the methods of producing same. More particularly, it pertains to the tertiary phosphoric acid esters of 5 aliphatic nitroalcohols.

My new phosphoric acid esters of aliphatic nitroalcohols may be represented by the followins structural formula:

in which R, R1, Ra, Ra, R4, and R5 may be either an alkyl or H. All of the W5 may be the same alkyl and the corresponding R. on each carbon atom may be the same alkyl but different from 25 that represented by the other R attached to the same carbon atom in cases where this second F. represents an alkyl instead of an H.

The phosphoric acid esters of the aliphatic nitroalcohols are preferably produced by reacting 50 an aliphatic nitroalcohol with phosphorus oxychloride, or with phosphorus pentachloride followed by subsequent treatment with water and suitable methods of obtaining them by both of these means are described below, but it is un- 85 derstood, of course, that my invention is not limited to these particular procedures.

The tertiary phosphoric acid esters of primary aliphatic alcohols have usually been prepared by reacting an excess of the aliphatic alcohol 40 with phosphorus oxychloride at low temperatures to produce the di-substitution products, followed by heating at relatively elevated temperatures to produce the trl-substituted product. In such processes it has customarily been necessary to 45 carry out the operation in such a manner as to remove from the zone of the reaction the byproduct hydrogen chloride as it is formed in order to prevent it from entering into various undesirable side reactions. The initial stage 50 the reaction, as has previously been indicated, must be effected at low temperatures in order to reduce the tendency toward the formation of undesired products, and recently it has been discovered that by similarly carrying out the second 56 stage of the reaction at low temperatures over longer periods of time, improved results are obtained in the form oi better yields of the desired products.

I have now discovered that while the primary aliphatic nitroalcohols do not ordinarily react with phosphorus oxychloride, even at room temperature, whereas corresponding aliphatic alcohols react with violence at sub-zero temperatures, reaction may be effected at temperatures of about 50 C. and above, although even at more elevated temperatures complete reaction is difllcuit to effect, the third chlorine ot the phosphorus oxychloride being quite unreactive toward such nitroalcohols.

A more satisfactory method of producing the phosphoric acid esters of the aliphatic nitroalcohols is by reacting the latter with phosphorus pentachloride. While the mechanism of the reaction is not definitely known, it apparently proceeds as follows: ROH+PCls- (RO) PCli-i-HCI. Where three or more moles of the nitroalcohol are present (RO)3PC12, and perhaps even (ROnPCl and/or (R0) 5P, may be formed. When any one of the last three compounds is treated with water, a tertiary phosphate, (ROMPO, isformed and hydrogen chloride and/ or the nitroalcohol is liberated.

The following specific examples illustrate suitable methods of obtaining my new phosphoric acid esters of primary aliphatic nltroalcohols:

Example 1 One mole ol 2 methyl 2 nitro l butanol (133 g.), 0.2 mole of phosphorus oxychloride (30.6 g.) and 135 g. of anhydrous carbon tetrachloride were placed in a reaction vessel equipped with a reflux cond nser. 0n heating the reaction mixture the evolution of the hydrogen chloride began as the boiling point of the carbon tetrachloride was reached and the reaction was continued by maintaining the reaction mixture in a state of mild reflux, i. e., '74-'76 C. At the end of 2 hours refluxing, the evolution of hydrogen chloride had practically ceased. The carbon tetrachloride was then distilled from the reaction mixture and the residue finally heated to 140 C. and then subjected to vacuum distillation to remove any unreacted 2-methyl-2- nitro-l-butanol. The residue left in the distillation kettle after heating to 150 C. at mm. constituted 81.5 g. of a cherry red liquid, which was dissolved in ether and washed with water. The ether layer was next washed with sodium bicarbonate solution and after the evolution of carbon dioxide, due to the presence of any acid bodies resulting from incomplete esteriflcation of a part of the phosphorus oxychloride, was complete, washed with water until neutral. and finally dried with anhydrous calcium chloride and decolorized with activated carbon. Aiter evaporation of the ether, 24.5 g. of practically colorless liquid was obtained which constituted a 28% yield of tertiary phosphate of 2-methyl-2- nitro-l-butanol, based on the phosphorus onchloride.

Example I! A solution of 240 g. 01 2-methyl-2-nitro-1- butanol (1.8 mole) and 150 g. of anhydrous carbon tetrachloride was placed in a reaction vessel provided with a reflux condenser, the reaction mixture cooled to 10 C. and the pressure in the reaction vessel reduced to l00150 mm. of mercury. To the reaction mixture was then slowly added 62.5 g. of phosphorus pentachloride (0.3 mole) over a period of approximately 2 hours. Reaction oi the phosphorus pentachloride with the nitroalcohol was very vigorous, all of the solid going into solution at this temperature. The reaction mixture was then slowly heated to the reflux temperature of the carbon tetrachloride, i. e., 44-45 C. After a relatively short period 01 time at this temperature, the evolution of hydrogen chloride ceased. The contents of the reaction vessel were then poured into water and thoroughly mixed. The oil layer was separated and washed with sodium bicarbonate solution. After washing until neutral, the carbon tetrachloride was removed by distilling at atmospheric pressure, followed by removal or the unreacted 2-methyl-2- nitro-l-butanol by distillation at 2 mm. of mercury. The residue was a light yellow viscous liquid which was easily decolorized by activated carbon giving a yield of g. 01 pure tertiary phosphate of 2-methyl-2-nitro-1-butanol, i. e. 99% of theory. If desired, this product can be crystailized by precipitation with petroleum ether from its absolute alcohol solution at approximately 0 C. Crystallization, however, ordinarily is not necessary in order to obtain a reasonably pure product. The tertiary phosphate of 2- methyl-2-nitro-1-butanol melts at 23-25 C., has a specific gravity of 1.2223 at 30/4 C. and when super-cooled to 20 C. has a refractive index of 1.4647. It is quite stable thermally, decomposition when heating at 1 mm. of mercury not taking place appreciably until a temperature of 250 C. has been reached. It is miscible with the usual oxygenated organic solvents and aromatic hydrocarbons; it is immiscible with water and only very slightly soluble in petroleum naphtha. On account of its low volatility and its compatibility with cellulose esters, it is an excellent plasticizer for such compositions.

Example III A solution of 71.5 g. (0.6 mole of 2-methyl-2- methyl-Z-nitro-l-propanol in cc. of anhydrous 2-nitropropane was placed in a reaction vessel equipped with a reflux condenser. To the reaction vessel while maintaining the contents thereof at a temperature of 10 C. was then slowly added 31.5 g. of phosphorus pentachloride (0.15 mole). The reaction mixture was then heated at 40 C. until evolution of the hydrogen chloride ceased. The 2-nitro-propane was evaporated under a partial vacuum and the white solid obtained slurried with water, followed by dilute sodium bicarbonate treatment and then purified by further crystallization from butanol. The theoretical yield of the tertiary phosphate of 2- methyl-2-nitro-1-propanol was obtained. This compound melts at C., is quite stable thermally and is very soluble in the lower molecular weight oxygenated solvents, slightly soluble in butanol and benzol and insoluble in petroleum solvents and water.

In the specific examples described above, large excesses of the nitroalcohols have been employed. This, however, is not essential to the production of good yields oi the corresponding phosphates when using phosphorus pentachloride, but due to the viscous character of the reaction product near the end of the reaction it is highly desirable to ve present in the reaction mixture either a substantial excess of the nitroalcohol or else an inert solvent such as carbon tetrachloride, nitroparaiilns or other similar materials which are not afl'ected by either the reactants or the products of the reactions and from which the reaction product may be readily separated. And in cases where the nitroalcohols used are high melting solids. as 2- methyl-2-nitro-l-propanol, an inert solvent is necessary regardless of the amount of excess nitroalcohol or or otherwise suitably removing it from the zone of reaction prior to heating the reaction mixture substantially above the temperature at which the solution of the phosphorus pentachloride is effected.

While I have only specifically described the production of the tertiary phosphates oi 2-methyl-2- nitro-1-propanol and 2-methyl-2-nitro-l-butanol, the same general procedure is applicable to the production of phosphates of other primary nitroalcohols as well as the homologs of these compounds, as for example, the tertiary phosphates of 2-nitro-1-propanol, Z-nitro-I-butanol, 2-nitrol-pentanol, etc.

Now having disclosed my invention, what I claim is:

1. Tertiary esters of phosphoric acid oi the general formula:

where R, R1, R2, R3, R4, and R5 are members selected from the group consisting of alkyl and H.

2. Tertiary esters of phosphoric acid of the general formula:

where R, R2, and R4 are the same alkyl and R1, phosphoric acid esters or primary aliphatic nitro- Ba, and! are the same alkyl which may be difieralcohols, the steps which comprise reacting with cut from the alkyl represented by R, R: and R4. phosphorus pentachloride a primary aliphatic 3. The tertiary ortho phosphate of 2-methyl-2- nitroalcohol having the nitro group attached to 5 nltro-i-propanol. the second carbon atom and treating the result- I 4. The tertiary ortho phosphate of 2-methyl-2- ins product with water. nitro-l-butanol.

5. In a process for the production of tertiary BYRON M. VANDERBILT.

CERTIFICATE OF CORRECTION. Patent No. 2,177,757. October 51, 1959.

BYRON ii; VANDERBILT.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, first column, lines 61 and 62, for "Z-methyl-2-methyl-2-nitro-1propano]:'f read Z-methyl-2-nitro-1-propanol; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 16th day of January, A. D. 191 .0.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

where R, R2, and R4 are the same alkyl and R1, phosphoric acid esters or primary aliphatic nitro- Ba, and! are the same alkyl which may be difieralcohols, the steps which comprise reacting with cut from the alkyl represented by R, R: and R4. phosphorus pentachloride a primary aliphatic 3. The tertiary ortho phosphate of 2-methyl-2- nitroalcohol having the nitro group attached to 5 nltro-i-propanol. the second carbon atom and treating the result- I 4. The tertiary ortho phosphate of 2-methyl-2- ins product with water. nitro-l-butanol.

5. In a process for the production of tertiary BYRON M. VANDERBILT.

CERTIFICATE OF CORRECTION. Patent No. 2,177,757. October 51, 1959.

BYRON ii; VANDERBILT.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, first column, lines 61 and 62, for "Z-methyl-2-methyl-2-nitro-1propano]:'f read Z-methyl-2-nitro-1-propanol; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 16th day of January, A. D. 191 .0.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

